The present invention relates to magnetic data storage systems. In particular, the invention relates to a magnetic write head pole (writer pole) used in such systems.
Magnetic heads mounted on a magnetic disc drive are required to provide larger magnetic fields with higher gradient for magnetic recording at higher density. More recent magnetic heads combine both a magnetoresistive (MR) or giant magnetoresistive (GMR) element for reading information from a magnetic medium and an inductive element for writing information to such a magnetic medium. Such magnetic heads are typically referred to as composite thin film magnetic heads or merged MR heads. The magnetic head is mounted or embedded in a slider which is supported in transducing relationship with respect to a magnetic medium.
The inductive write head element includes first and second poles which have first and second pole tips respectively. The pole tips are separated by a gap at an air bearing surface (ABS) or head surface. A coil is positioned between the first and second poles. Information is written on the magnetic medium at the first and second pole tips.
Flux density, which is a measure of the quantity of magnetism, needs to be high in the inductive head element for it to provide a high magnetic field for writing. There are limitations to the capability of the inductive head element to provide high flux density since materials have a saturation level beyond which they will conduct no more flux. Similarly, magnetic moment, which is a measure of the strength of the magnet, does not change beyond a certain level (reaches saturation) even if the strength of the applied magnetic field is increased. A high saturation magnetic moment is very desirable for write heads recording at high areal densities, the areal density being the amount of data that can be squeezed on to a given area of the magnetic medium. Further, finite element modeling or analysis of magnetic recording indicates that a high saturation magnetic moment is particularly critical for those magnetic layers adjacent to the non-magnetic gap layer of the write head.
The use of materials with high magnetic moment for writer pole tips allows for the generation of higher magnetic fields in the magnetic media, larger field gradients, and faster effective rise times. Improvements, such as narrower pulse widths, smaller erase bands, and straighter transitions for given media properties are possible if materials with high magnetic moment are used for the poles. In addition, increased over-write (OVW) on magnetic media having high coercivity can also be achieved with high moment poles. OVW, expressed in dB, is a measure of how well prior recorded information can be erased by over writing the medium with a different signal. All the above advantages become even more important at high areal densities of magnetic recording.
The prior art teaches that in order to practically achieve a higher field in the gap, a seed and/or capping layer can be used adjacent to the gap to minimize saturation of pole tips and produce a higher gap field. Further, the prior art suggests that all of the individual magnetic layers utilized in the write head should possess high magnetic permeability and moderately soft magnetic properties in addition to a desirable saturation magnetic moment. Prior art write heads have employed individual layers of magnetic materials that each possess a combination of the above desirable properties, thereby limiting the choice of the saturation magnetic moment level to materials that have high magnetic permeability and moderately soft magnetic properties.
The present invention addresses these problems, and offers other advantages over the prior art.
The present invention relates to data storage systems that include a magnetic head with at least one pole having a seed layer made of a material with a low permeability by itself and a high saturation moment magnetically coupled to an adjacent high permeability layer which causes the permeability of the seed layer material to increase, thereby addressing the above-identified problems.
A magnetic head in a magnetic storage system is provided in which materials that do not individually display high permeability and low coercivity are satisfactorily employed in a write head when coupled to adjacent high permeability layers. The magnetic write head includes a gap layer which separates a pair of poles. At least one pole of the pair of poles includes a pole layer formed of a high permeability material and a seed layer adjacent to the pole layer. The seed layer is formed of a high moment low permeability material having a high saturation magnetic moment greater than about 2.1 Tesla and a low permeability of about 10-100. The high permeability material of the pole layer causes the permeability of the adjacent seed layer to substantially increase from about 10-100 to about 1400-1600, thereby providing a pole with high permeability and high saturation moment. In addition, a method of forming a magnetic head for use in a magnetic storage system is provided.